PHP Ternary operator ('shorthand' if-statement)

Question

I've reviewed the PHP Manual here: #3 ternary operators

but I don't understand why all three of these don't function as expected:

   $a = array('a','b','c');

    //works
    if(isset($a)){echo "yes";} else {echo "no";}

    //works 
    isset($a) == true ? $answer = "yes" : $answer = "no";
    echo $answer;

    //does not work
    isset($a) == true ? echo "yes" : echo "no";

Thank you for your consideration.

Barmar · Accepted Answer · 2016-04-18 22:13:35Z

4

Since the ternary expression is an expression, its operands have to be expressions as well. echo is not an expression, it's a statement, it can't be used where expressions are required. So the last one doesn't work for the same reason you can't write:

$a = echo "abc";

answered Apr 18, 2016 at 22:13

Barmar

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6 Comments

n8thanael Over a year ago

Thanks for the insight.. so it seems like it differs a lot from the regular 'non-shorthand' If statement? if ($a = "abc") "statement" else "statement" vs. shorthand if-statement: statement: $a = "abc" ? "statement" : "statement" --- I guess after reading the documentation I thought they were very similar - but they aren't.

n8thanael Over a year ago

@Robert...this does infact work just fine...thanks: echo isset($a) ? "yes" : "no";

Barmar Over a year ago

@n8thanael The point is that you can use a regular if statement anywhere you can write a statement, and you can use a ternary expression anywhere you can write an expression.

Barmar Over a year ago

And the body of an if can be any statement, while the operands of ternary can be any expression.

Barmar Over a year ago

@pmirnd Yes. An expression can be used wherever a statement is required, but not vice versa.

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Amous · Accepted Answer · 2016-04-18 22:05:02Z

1

Rewrite the statement as,

echo isset($a) == true ? "yes" : "no";

The ternary operator doesn't exactly function like an if statement. The ternary operator does not execute the 2nd or 3rd expressions, it returns it.

edited Apr 18, 2016 at 22:05

answered Apr 18, 2016 at 21:59

Amous

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Comments

kay27 · Accepted Answer · 2016-04-18 21:56:56Z

0

The correct way is:

echo isset($a) == true ? "yes" : "no";

Also no need to compare it with true:

echo isset($a) ? "yes" : "no";

answered Apr 18, 2016 at 21:56

kay27

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Comments

Robert · Accepted Answer · 2016-04-18 22:00:47Z

0

Because when you use ternary operators you need to count operators precedence and associativity

you can rewrite your code to

echo isset($a) ? "yes" : "no";

answered Apr 18, 2016 at 22:00

Robert

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Comments

merdincz · Accepted Answer · 2016-04-18 22:00:47Z

0

Your last line of code should be like;

echo isset($a) == true ?  "yes" :  "no";

answered Apr 18, 2016 at 22:00

merdincz

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